Can Adults Develop ADHD?

Over the past two decades, diagnoses of attention deficit hyperactivity disorder (ADHD) in children have almost doubled in the U.S., from about 6 percent to more than 10 percent, according to a recent study in JAMA Pediatrics. Traditionally viewed as a neurodevelopmental disorder, ADHD typically appears before adolescence and often resolves by adulthood. But an increasing number of young and even middle-aged adults are also being diagnosed for the first time. Is adult-onset ADHD for real?

Characterized by such symptoms as impulsivity, high distractibility, inability to pay close attention to details or organize tasks, forgetfulness, fidgetiness, excessive talking, and “bouncing off the walls” energy, ADHD is a real diagnosis, but one that exists on a continuum.

According to the criteria of the Diagnostic and Statistical Manual (DSM-5, the “bible” of psychiatry), at least some symptoms of hyperactivity and inattentiveness must be present before age 12, meaning that by definition, ADHD cannot be diagnosed in adults who have no history of any of its symptoms. But that idea is now being challenged in what some researchers are calling a paradigm shift in the understanding of the disorder.

First-time ADHD onset in adults?

A few population-based studies in recent years add some weight to the notion that ADHD can develop in adulthood rather than just persist from childhood (though the studies are problematic in some ways, and not all the research supports this contention, as discussed below). A 2016 study in JAMA Psychiatry, which followed more than 4,000 Brazilians from ages 11 to 18 or 19, found that 9 percent were diagnosed with ADHD at baseline. By the end of the study, 12 percent of them overall met the criteria—but most of them (87 percent) did not have ADHD as children, which suggests “the existence of 2 syndromes that have distinct developmental trajectories, with a late onset far more prevalent among adults than a childhood onset,” the researchers concluded.

Another study in the same issue of JAMA Psychiatry followed more than 2,200 twins in the U.K. from ages 5 to 18. Of the 247 individuals who were diagnosed with childhood-onset ADHD, 54 (22 percent) continued to meet the criteria for the condition at age 18. On the flip side, of the 166 individuals diagnosed with ADHD as young adults, 112 of them (67 percent) did not meet the criteria for ADHD as children at any of the four previous evaluations. The authors concluded that “adult ADHD is more complex than a straightforward continuation of the childhood disorder.”

These two studies followed a 2015 study in the American Journal of Psychiatry, which tracked 1,000 people in New Zealand from ages 3 to 38 and found that 90 percent of adults presenting with ADHD did not have a history of childhood ADHD. The re­­searchers concluded that “adult ADHD is not a neurodevelopmental disorder,” meaning it has a different cause than childhood-onset ADHD.

Of note, regardless of whether ADHD persists from childhood or begins in adulthood, adult symptoms may differ from those seen in children. Children with ADHD typically have hyperactivity symptoms, such as running and jumping around a lot. More common in adults is inattentiveness, including trouble concentrating or being forgetful. And when adults with ADHD do have hyperactivity, it’s more a feeling of mental as opposed to physical restlessness. Also, though more boys than girls present with ADHD as children, the sex ratios are closer to equal in adulthood.

Is it ADHD, or something else?

But the studies tend to have methodological limitations, including that the adult diagnoses were based on self-report of symptoms, while childhood diagnoses were based on reports from parents or teachers, which could overestimate the number of adult-onset cases. Notably, the Brazilian and U.K. studies did not look at adults beyond their late teen years—which is at best “too small a slice of adulthood” from which to draw firm conclusions, the accompanying editorial pointed out.

Moreover, in a study published in 2018 in the American Journal of Psychiatry, researchers were more skeptical, calling most cases of adult-onset ADHD “false positives.” It followed 239 children without ADHD at baseline, carefully evaluating them at eight separate points over 14 years until they reached their mid-twenties. While a few of the cases of adult-onset ADHD were found to be “valid,” most could be fully or largely ex­­plained by other mental disorders or substance use.

Even the researchers of the Brazilian and U.K. studies noted that many cases of supposed adult-onset ADHD may be a different mental health condition altogether, such as anxiety, depression, or obsessive-compulsive disorder. It’s also possible, they say, that in some cases, ADHD may be masked in childhood due to protective factors, such as having high cognitive skills and a supportive family, which allow children to cope with or compensate for the symptoms—but when they, as adults, are faced with more life challenges and a less-structured environment, the symptoms may then become apparent. That is, ADHD that appears for the first time in adulthood may just be “late-identified.”

Bottom line: Research is still ongoing about whether ADHD can begin in adulthood as a distinct disorder from childhood-onset ADHD. One sure thing is that if true adult-onset ADHD exists, it is not as common as it has recently been made out to be. Still, adults who have long-standing impulsivity, hyperactivity, or inattentiveness that is impairing their ability to function well in daily life should be evaluated, even if they don’t recall being that way early in life or if family members say these symptoms were not apparent during childhood.

But it’s key for health care providers to determine whether the symptoms may be related to some other mental health condition before beginning treatment, which often involves use of the prescription stimulants methylphenidate (Ritalin) and dextroamphetamine (in Adderall), plus behavioral treatments for children and cognitive-behavioral treatments for adults. For most individuals with ADHD, this combination of pharmacologic and psychosocial interventions is optimal. The CDC outlines the criteria used to diagnose ADHD in both children and adults on its website.